Exact same problem here... this is an issue. Requesting an update brings up the update window which states:
"Initializing, please wait..."
and there it stays forever, doing nothing. Overall progress never begins.
Program update feature does the same thing.
WinXP SP3
Comodo Firewall (allowing all Avast! events; also tried with firewall turned off)
Obviously, an antivirus that won't update is going to be a big problem.